Studies on the origin of the glycerol and fatty acid moieties of the accumulated triglycerides and the structural polar lipids of cultured mammalian cells will be contined. The contribution of monoglycerides to these two classes of lipids, using their radioactive 1- and 2-monoether analogues will be extended and the oxidation of the latter compounds to vinyl ethers and esters will be examined. The uptake and oxidation of fatty acids as a function of triglyceride accumulation by "high lipid" and "low lipid" cells will be examined employing radioactive precursors with serum containing and erum free media.